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allow-with-flags.md

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Allow with specified parameter flags only

Some functions can be called with flags or bitmasks, for example

json_encode($foo, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT);

Let's say you want to disallow json_encode() except when called with JSON_HEX_APOS (integer 4) flag. In the call above, the value of the second parameter (JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT) is 13 (1 | 4 | 8). For the extension to be able to "find" the 4 in 13, you need to use the ParamFlags family of config options:

  • allowParamFlagsInAllowed
  • allowParamFlagsAnywhere
  • allowExceptParamFlagsInAllowed or disallowParamFlagsInAllowed
  • allowExceptParamFlags or disallowParamFlags

They work like their non-flags Param counterparts except they're looking if specific bits in the mask parameter are set.

The json_encode() example mentioned above would look like the following snippet:

parameters:
    disallowedFunctionCalls:
            function: 'json_encode'
            allowParamFlagsAnywhere:
                -
                    position: 2
                    value: ::JSON_HEX_APOS

Just like with regular parameters, you can also use typeString instead of value. The extra bonus this brings is unions: if you want to (dis)allow a parameter when either the flag 1 or 2 is set, use typeString: 1 | 2. Note that the | operator here is not the PHP's bitwise or operator.